More than 100 years ago, the famous physicist Ernst Abbe described a fundamental limitation of any microscope that relies on any lens or system of lenses in an imaging system to focus light or other radiation: diffraction obscures (makes fuzzy) those details of the image that are smaller in size than approximately one-half the wavelength of the radiation. See "Scanned-Probe Microscopes" by H. Kumar Wickramasinghe, published in Scientific American, Vol. 261, No. 4, pp. 98-105 (October 1989). In other words, the resolution of the microscope is limited by the wavelength of the radiation. In order to circumvent this limitation, researchers have investigated the use of inter alia, involving "near-field scanning optical microscopy" (hereinafter "NSOM") devices. These devices typically comprise an aperture located at the tip of an elongated optical probe, the aperture having a (largest) dimension that is smaller than approximately the wavelength of the optical radiation being used, positioned in close proximity to the surface of a sample body; and the aperture is allowed to scan (move) laterally (in one or two dimensions) across the (irregular) surface of the sample body at distances of separation therefrom all of which distances are characterized by mutually equal force components exerted on the probe device in the direction perpendicular to the global (overall) surface of the sample body, the scanning being detected and controlled by an electromechanical feedback servomechanism.
For example, U.S. Pat. No. 4,604,620 inter alia describes a probe device having an aperture located at the tip of a cladded glass fiber that has been coated with a metallic layer. The aperture is drilled into the metallic layer at the tip of the fiber at a location that is coaxed with the fiber. The (immediate) neighborhood of the tip is composed of a section of solid glass fiber that has obliquely sloping (truncated conical) sidewalls, whereby the sidewalls do not form a cylinder of any kind. Therefore, as the probe device laterally scans a rough surface, the calculations required to determine the desired information on the actual contours (actual profile) of the surface of the sample body require prior detailed knowledge of the slanting contours of the sidewalls of the probe, and these calculations typically do not yield accurate metrological determinations of the desired profile of the contours of the surface of the sample body, especially at locations of the surface of the sample body where sudden jumps (vertical steps) thereof are located. In addition, fabrication of the probe device is complex and expensive, especially because of the need for drilling the aperture coaxially with the fiber.